»Magnesium Sulfate,rendered anhydrous by ignition,contains not less than 99.0percent and not more than 100.5percent of MgSO4.

Packaging and storage
Preserve in well-closed containers.

Labeling
The label states whether it is the monohydrate,the dried form,or the heptahydrate.Magnesium Sulfate intended for use in preparing parenteral dosage forms is so labeled.Magnesium Sulfate not intended for use in preparing parenteral dosage forms is so labeled;in addition,it may be labeled also as intended for use in preparing nonparenteral dosage forms.

Loss on drying á731ñ
Dry it at 105for 2hours:the anhydrous form loses not more than 2%of its weight.

Loss on ignition á733ñ
Weigh accurately about 1g in a crucible,heat at 105for 2hours,then ignite in a muffle furnace at 450±25to constant weight:the monohydrate loses between 13.0%and 16.0%of its weight,the dried form loses between 22.0%and 28.0%of its weight,and the heptahydrate loses between 40.0%and 52.0%of its weight.

Ammonium acetate solution
Transfer 250g of ammonium acetate to a 500-mLvolumetric flask,dissolve in and dilute with water to volume,and mix.

Ascorbic acid solution
Transfer 1.34g of ascorbic acid to a 100-mLvolumetric flask,dissolve in and dilute with water to volume,and mix.Use this solution on the day prepared.

Color reagent
Transfer 380mg of 3-(2-pyridyl)-5,6-di-(2-furyl)-1,2,4-triazine-5¢,5¢¢-disulfonic acid,disodium salt to a 100-mLvolumetric flask,dissolve in Ammonium acetate solution,shaking by mechanical means if necessary,dilute with Ammonium acetate solutionto volume,and mix.Use this solution on the day prepared.

Procedure
To each of the flasks containing the Standard preparations,the Test preparation,and the Blank,add 5mLof Ascorbic acid solutionand 5mLof Color reagent.Dilute each solution with Dilute hydrochloric acidto volume,mix,and allow to stand for 10minutes.Concomitantly determine the absorbances of the solutions from the Standard preparationsand the Test preparationat the wavelength of maximum absorbance at about 594nm,with a suitable spectrophotometer,using the solution from the Blankto set the instrument to zero.Plot the absorbance values of the solutions from the Standard preparationsversus their iron contents,in µg per 50-mLvolumetric flask,and draw the straight line best fitting the three plotted points.From the graph so obtained determine the iron content,C,in µg per 50-mLvolumetric flask,of the solution from the Test preparation.Calculate the content,in ppm,of iron in the portion of Magnesium Sulfate taken by multiplying Cby 0.1:the limit is 0.5µg per g.